Phytochemicals Against Drug-Resistant Bacterial Biofilms and Use of Green Extraction Solvents to Increase Their Bioactivity.

Antimicrobial resistance has become one of the major global public health issues of the twenty-first century. One of the main factors in the limited action of antimicrobials is related to the ability of microorganisms, particularly bacteria, to form biofilms. These complex and well-organized communities allow the colonizing cells to acquire survival advantages over the same cells in suspension, including antibiotic resistance. A huge percentage of bacterial infections in humans are associated with biofilms, and many of them are chronic. Therefore, there is an urgent need to develop new products effective in controlling or eradicating biofilms. Plant secondary metabolites (phytochemicals) have demonstrated their potential as antibacterials against planktonic cells and sessile communities when used alone or in synergy with other molecules. This chapter covers recent advances in the activity of phytochemicals against biofilms, particularly those formed by drug-resistant bacteria. In addition, taking into account that the extraction step is crucial for the successful development of new bioactive compounds, the use of novel solvents that increase the phytochemical effect, such as natural deep eutectic solvents (NADES), as well as the recent applications of these solvents as antimicrobials are discussed.